DEVELOPMENT OF MULTIMETER … From what it was, to what it is!

The innovation of test and measuring started when, from simple voltmeter and ampere meters, the instruments started doing multitasking. The same instrument being used to measure voltage, ampere and resistance gave birth to the term multimeter, where one meter can be used in multiple applications.

When the multi-tasking meters were first made, they had all analogue movements, and they were displayed on anti-parallax scales by needles on a dial marked for various ranges. The first step of innovations started when these analogue scales were replaced by LCD displays. This made the meters easy to use where you just had to read the digits rather than counting on the scale and not getting an exact value.

The next change in the multimeter came when parameters like frequency, capacitance, temperature and duty cycle could be measured. Along with this the instruments were then used for testing transistors and diodes.

With these innovations, the standard to which these meters were built also increased. With the increase in the standards the meters started getting manufactured according to the guidelines of UL, CE and IEC standards.

With these standards any openings in the meters that were not used other than the terminal inputs had to be removed and hence the transistor testing sockets became non-existent on higher end models that adhered to these standards.

The other innovation came when users started using the meters at places where pure sine waves were not available. This led the engineers to develop the method of sampling waveforms where they could measure the amplitude irrespective of the wave shape. This led to the invention of RMS / T-RMS multimeters.

With more machines coming in the industries and in office environments, the need to measure electrical parameters like voltage and current over a wide frequency bandwidth became a compelling application for engineers to develop multimeters that could measure these parameters up to 1kHz bandwidth and in some cases even up to 200kHz bandwidth.

With the advent of micro-controller and micro-processor technology it is not possible to store the measured data for future reference, record the variation of parameter with respect to real time applications thus began the era of the multimeter becoming an analytical instrument and the age of combining more products and functions in one unit started.

Today we not only have a multimeter but we also have a multimeter with a built in digital storage oscilloscope. The trend capture facility, helps in displaying the variation in parameters with respect to real time variations. We further added internal memory to do data logging in the instrument.

In some site of applications the users wanted to record the data in real time on their PC or in their PLC systems, so we at CEM developed multimeters with wireless PC interface. Where you can record the data on your PC in real time without any physical connection to the PC (WIRELESSLY).

After this started the age of the smartphones and Cloud storage. Nobody wants data to be constrained to a particular device and everybody wants data available at any given point in time where ever they want it. We found a way out for this.

What we first did was we added Bluetooth function to the multimeter. With this Bluetooth we could connect the multimeter to the smartphone or the PC. Using this Bluetooth we can show all the readings displayed on the meter, in the smartphone display itself. This helped us to store the data being shown on the smartphone in the cloud service provided by the smartphone manufacturer. Thereby making seamless wireless connection to the smartphone and communicating data with it for storage or to transfer the data over internet to some other remote location.

All of this we did in CEM. From developing a multimeter with inbuilt data storage capability, to wirelessly transfer the date to the PC and to show the data on smartphone and store it on to the cloud.

Out model DT-989 is a 50,000 count multimeter with trend capture facility and has blue tooth connection for wirelessly transferring the data on to PC or smartphone. The display of the multimeter is replicated on the smartphone display. As soon as you move the smartphone from portrait display more to landscape mode, Trend capture can also be seen. Over and above we have put in a TFT color display to this multimeter. With the TFT display you have up to 160 degree viewing angle. So you can keep multimeter at whatever angle and yet see the display without it being distorted.

In our model DT-9929 with the 40,000 count display we have inbuilt memory to record the data. However in our models DT-9939 and DT-9959 you can transfer this measured data wirelessly to your PC.

In the model DT-9979, we have Bluetooth interface for PC or Smartphone connection and it also has bandwidth of 100kHz for measuring voltage and current. In the model DT-9987, to what ever is available in DT-9979 we added a color TFT display for better and clear viewing angle.

DT-9989 has all of the above and a built-in 10MHz Digital Storage Oscilloscope with colored display. This instrument can be used as a data logger, multimeter and a digital storage oscilloscope. On top of this, with blue tooth connection it has become very easy to store, or communicate measured data over internet or on to a smartphone / PC.

There are various applications of a multimeter. Right from measuring the incoming voltage to the voltage and current consumption of loads can all be measured. One of the most compelling application of the multimeter is to measure the voltage of Variable Frequency Drive

A true-RMS DMM will give an accurate reading of the heating effect of the non-sinusoidal voltage applied to the motor, but will not agree with the motor controller’s output voltage reading which is displaying the RMS value of the fundamental component only (typically from 30 Hz to 60 Hz). The issues are bandwidth and shielding. Many of today’s true RMS digital multimeters have a wide bandwidth, sometimes out as far as 200 kHz or more, which allows the meter to respond not only to the fundamental component that the motor really responds to, but also to all of the high frequency components generated by the PWM drive. In addition, if the multimeter is not shielded for high frequency noise, this can also lead to poor measurement performance due to the high noise levels generated by the drive controller.

Because of their higher bandwidth and shielding issues, many true RMS meters will display readings as much as 20 to 30 % higher than the drive controller is indicating. CEM’s new DT-9979, DT-9987 and DT-9989 series of multimeters, has the ability to display multiple parameters at the same time and utilize the selectable low pass filter, giving the troubleshooter or engineer the ability make accurate voltage, current and frequency measurements on the output side of the drive either at the drive itself or at the motor terminals and also display the filtered output voltage and frequency (motor speed) simultaneously. With the filter selected, the readings for both voltage and frequency (motor speed) should now agree with the associated drive control display indications if they are available.

Over and above all these instruments are built with full safety precautions keeping in mind the latest CAT IV specifications, the latest IEC standards and is TUV GS certified. We also provide INGRESS PROTECTION to most of our multimeters. Thereby making the meters water proof and dust proof to work in compelling conditions.

Our multimeters confirms to CAT III 1000V and CAT IV 600V. What does this CAT mean?

Measurement Category IV: This category refers to origin of installation or utility level measurements on primary over-current protection devices and on ripple control units.

All the meters that CEM sells carry a warranty against any manufacturing defects. This hassle-free warranty allows the customer to get the instrument replaced within an unparalleled record period of 48 hours. The conditions of warranty are however, mentioned on the website www.cem-instruments.in

All these products are available directly from CEM’s office at Kolkata. Along with normal sales channels, CEM will also be pursuing online sales via all leading e-commerce portals like Tolexo, Paytm, Urjakart and Industry buying. All CEM product details and catalogues are available on its website www.cem-instruments.in. CEM can be reached at info@cem-instruments.in